Die process or method



Feb. 9, 1960 MT. STAMPER 2,924,701

DIE PROCESS 0R METHOD Filed Dec. 20, 1957 3 Sheets-Sheet 1 INVENTOR.

ATTORNEY 1960 M. T. STAMPER 2,924,701

DIE PROCESS OR METHOD Fiied Dec. 20, 1957 I5 Sheets-Sheet 2 SUPPLY INVENTOR.

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Feb. 9, 1960 M. 'r. STAM PER DIE PROCESS OR METHOD 3 Sheets-Sheet 3 Filed Dec. 20, 1957 INVENTOR. BY vhzffmyvz ATTORNEY I AIN'- Va United States Patent OfiFice DIE PROCESS R METHOD Malcolm T. Stamper, Grosse Pointe, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 20, 1957, Serial No. 704,200

Claims. (Cl. 219-69) The invention relates to a process or method of making permanent dies. It is particularly useful in making permanent blanking dies which are used to form blanks from sheet stock.

The art of tool and die making has been a long established one and has acquired a status such that those who desire to practice the art must serve a long apprenticeship and have several years experience before they may be considered fully qualified. The practices and techniques generally found in tool and die making are commonly passed from journeyman to apprentice and may vary considerably from shope to shop. Much of the work involved includes the techniques of working and heat treating materials. The dies are usually finished by hand, requiring long hours of tedious work which can only be done in a satisfactory manner after much experience. As a result, the cost of obtaining permanent die sets is based primarily upon the labor involved rather than the materials used.

It is now proposed to provide processes and methods by which permanent die sets may be manufactured which are fully equal in quality, and in many instances superior, to dies made by previous practices. Basically, the invention includes the making of an electrode quickly, inexpensively and accurately, electro-eroding a die punch with this electrode, electro-eroding a second electrode formed as is the die punch, and using the second electrode to electro-erode a die from die stock. By use of such a process, the time consumed in making a die set comprised of a die and a die punch may be reduced so that the overall cost of the die set is about one-third of the cost of making the same die set by previously known practices. The process maybe used to provide die strippers and shedders with little additional time and no additional work requiring great accuracy. The invention may be practiced by persons who are inexperienced in the tool and die making arts, yet their die products are found to be equal or superior in all respects to comparable dies made heretofore.

The preferred method of forming the inexpensive electrode includes adaptation of a process which has become known as the steel rule die process. This type of process is the subject of U.S. Patent No. 2,495,221, Berlin, for example. The process herein disclosed and claimed contemplates the use of metals other than steel which are easier'to form and also provide better electrode action. Brass is an excellent metal for this purpose, although other metals having the requisite characteristics may of course be used. Similarly, the die punch electrode is preferably formed from brass stock, but may also be formed of other metals.

In the drawings:

Figire l is a perspective view of the first steps used to form a brass electrode;

Figure 2 is a partial cross section view taken in the direction of arrows 22 of Figure 1;

Figure 3 is a perspective view of the completed electrode assembly;

2,924,701 Patented Feb. 9, 1960 Figure 4 is a partial cross section view taken in the direction of arrows 4-4 of Figure 3;

Figure 5 is a perspective diagrammatic view of the electrode of Figure 3 as installed in a press prior to the electro-erosion step of the process and having parts broken away and in section;

Figure 6 is a partial cross section view showing the electrode after the completion of the electro-erosion step with the electrode being partially retracted;

Figure 7a is a perspective view of die stock with a die punch and a die stripper formed therefrom in accordance with the invention;

Figure 7b is a perspective view of the electrode stock with a die punch electrode formed therefrom in accordance with the invention;

Figure 7c is a perspective view of die shedder stock with a die shedder formed therefrom in accordance with the invention;

Figure 8 is a diagrammatic perspective view of the die punch electrode in position prior to electro-erosion of the die and having parts broken away and in section;

Figure 9 is a partial section view of the die punch electrode and the die being eroded;

Figure 10 is a perspective view of the completed die and die punch formed by the process; and

Figure ll shows the die and die punch installed in a press.

The methods and processes constituting the invention may best be described while referring to the drawings. The figures of the drawings are arranged in the order in which the steps comprising the invention are preferably performed. As will be obvious, some of the steps may be performed at other stages than the order shown without departing from the invention.

If a blanking die is required for blanking workpieces having a predetermined shape, the blank is laid out as at 12, by well known layout techniques, on a wood shoe 14. This shoe is preferably diemakers plywood. The blank 16 is sawed out of the plywood shoe by use of a diemakers jigsaw 18. It is preferred that the blade of the jigsaw have the same width as the electrode stock to be used. It may, if desired, have a slightly narrower width to provide a more snug fit as will be described. The path 20 cut by the jigsaw blade will then be the same width as or slightly narrower than the width of the electrode stock to be used. When blank 16 is completely out out of shoe 14, it becomes a plug 22 which will be used in a manner to be described. The remainder of the plywood shoe 14, commonly referred to as the offal 24, is also to be used in the process.

Rule or shim stock 26 may be bent or otherwise formed to the dimensions of the blank to be made by the permanent die set by use of standard die-making tools. It may be made of one or more pieces of stock, the only requirement being that all pieces be electrically connected when the electrode is completed. This stock may be formed of any metal having suitable characteristics for an electrode to be used in the electro-erosion step of the process. It has been found that brass is an excellent material which may be easily and accurately bent to the proper form and may be obtained in a variety of sizes at a reasonable cost. The transverse width of the stock 26 must be sufficiently greater than the thickness of the plywood shoe 14 to permit the stock to extend beyond one surface of the shoe, as is shown in Figures 3 and 4, for example. The stock should extend sufficiently beyond the shoe surface to allow it to pass entirely through the materials to be electro-eroded, as will be later described.

The pro-formed electrode stock is fitted into the aperture formed in the offal 24 by the removal of plug 22. The plug is then inserted within the formed electrode to hold the electrode securely in place. An outline eleccuring means is disclosed in thediagrammatio views constituting Figures and 8 since suchmeans are well known in the art and may therefore be omitted forclarity;

The lower shoe 32 of the press 28 maybe provided with asuitable tank 34 whi'cll'cont'ains a dielectric fluid 36 of suflicient depth to" cover the shoe 32 and the die stock 3% to be worked. This die stock is secured in positionon shoe 32 and may be any of several metallic die stock materials; It may be hardened steel die" stock, stock which has not been hardened, carbide die stock, or other suitable materials. The process is not afiected by the fact that the diestock is hardened prior tothe electro-erosion step. It is, in fact, preferable that the diestock be ready inall respects for use upon completion of the electro-erosion process; This will eliminate the setting: up of unnecessary stresses by heat treating the material after shaping the die and will eliminate handling of soft dies and die punches after they have been formed to specification.

An el'ectro-erosion power supply 40 is connected'with electrode 26 and die stock 38. Any of several commercially available units may be used. Such power supply systems may be provided with variable controls which permit control of the die clearances obtained by controlling the amount of material electro-eroded in addition to that required for'passage ofthe electrode. The principles of controlling this factor are well known in the art of el'ectro-erosion.

The electrode 26 is lowered toward stock- 38 withthe electro-erosion power supply operative. The electrode will pass into and, if desired, through the-stock 38, eroding a smooth surface having accurately controlled dimensions. The stock 38' will thus be formed into a die punch 42 and the ofial may be used as a die stripper 44.

The die punch 42 and the die stripper 44- are then removed from the lower shoe s-zor the press and replaced by electrode stock 46 which may also bebrass if desired. The electro-erosion' operation is then repeated to form a second die punch 48 which will be used in a later step as an electrode.

lf it is desired to provide a die shedder, additional stock 43 may be placed on' the lower shoe 32in place of the material already shaped and the electro-erosion operation may be repeated to provide a shedder 45 having the same configuration as the die punch earlier formed; The shedder 45 may be made of any desirable metallic materials. Control of the electro-erosion power supply will permit the provision of greater clearances gained by passing the electrode 26 through the shedder stock to provide desirable clearances for the shedder 45 relative to the die to be formed in the next step.

The electrode 26 with its plywood shoe 14 is removed from upper shoe'30, and lower shoe 32 is also cleared. The punch electrode 48 is attached to the upper shoe of the press. If desired, it may be attached directly to the press shaft with requisite electrical insulation to separate it electrically from the press frame. A second plate 56 of die stock, whichmay' be identical to die stock 3?. previously used, is installed on lower. shoe 32. In order to expedite the next erosion; operation, plate 50 may be pro-trimmed asat52 to the approximate shape of the electrode 48.. A small amount of material should be leftwhich will be electro-eroded 'to form the die 54:- The assembly shown in 4 electro-erosion operation is againrepeated to form this die.

A die set has thus been made in accordance with the invention. The die set includes a die punch 42 and a die 5'4 which may be used in a press 56 having shoes 58 and 60. When desired, a die stripper 44 and a die shedder similar to the die punch may also have been formed and these elements may likewise be in press 56. The die set so formed isready for use immediately upon completion of the above operations if the stocks from which the die elements were made were hardened prior to the electro-erosion steps. The die set is equal or superior in every respect to permanent die sets made by prior practices. The electrodes may also be stored and used to provide additional die sets which will be identical to the first die set. It is therefore obvious that the ad ditional die sets obtained will be of equal quality and may bemanufactured in a very short period of time relative to the time: required to ma'keadditional die sets by prior methods; These additional die sets thushave the advantage of nominal cost coupled with the fact that they are. exact duplicates of the original set What is claimed is:-

l. A- method of making a permanent die set including a die punch, a die stripper,- and a die, said method comprising the'steps' of forming-an outline electrode, securing said electrodeto one shoe ofa' press and securing die stock to the other shoe of the press and submerging said die stock in dielectric fluid, passing said electrode through said die stock while said electrode and said'diestock are electrically energized from a high frequency power supply to erode said die stock and'simultaneously form a die punch from one portion of said die stock and a die stripper from the complementary portionof said die stock, similarly electro-ero'ding' electrode stock to form a die punch electrode, replacing saidoutline electrode with said die punch electrode and electro-eroding additional die stock to provide a die.

2. The method of making a permanent dieset including a die punch, a die stripper,a die shedder, and a die,

saidmethod comprising the steps of forming a metallic rule electrode and securing said electrode to one shoe of a press, securing die stock to the other shoe of the press" and submerging said die stock in dielectric fluid, electro-eroding said rule-electrode through said die stock to simultaneously produce a die punch and die stripper therefrom, electro-eroding electrode stock to produce a die punch. electrode, electro-eroding die shedder stock to produce a die shedder, replacing said rule electrode with said: die punch electrode and electro-eroding additional die stock to produce a die.

3. A method of making a permanent dieset comprising thesteps of making a blank layout on a sheet of diemakers' plywood, sawing out said blank layout to provide a' plywoodplug and oflal, bending brass rule stock to the form of said blank layout, inserting-said bent stock in said plywood oifal and said plywood plug in saidbent stock and positioning said plug in the plane of said oflal to hold said bent stock therein whereby an electrode assembly'is formed, securing the electrode assembly to one shoe of a press and securing die stockto the other shoe of the press and submerging said die stock in dielectric fluid, electro-eroding said bent stock through said die stock to-simultaneously form a die punch and a die stripper, replacing said die stock with brass electrode stock and electro-eroding said bent stock through said brass electrode stock to provide a brass die punch'electrode, electro-eroding said bent stock through die shedder stock to produce a die shedder, replacing said bent stock electrode with said die punch electrode, and electroeroding said die punch electrode through additional die stock to forma permanent die.

4. The method of making a permanent die setcomprising thesteps'of forming an outline electrode, electroeroding said outline electrode through hardened steel'die stock to simultaneously form a permanent die punch and die stripper, electro-eroding said outline electrode through electrode stock to form a die punch electrode, electroeroding said outline electrode through die shedder stock to form a die shedder and electro-eroding said die punch electrode through hardened steel die stock to form a permanent die.

5. A method of making a permanent die set comprising the steps of forming an outline electrode from brass shim stock, electro-eroding said outline electrode into die stock to provide complementary first and second die set elements, electro-eroding said outline electrode into electrode stock to form a second electrode having the same shape as said first die set element, and electroeroding said second electrode through additional die stock to form a third die set element complementary to said first die set element.

References Cited in the file of this patent UNITED STATES PATENTS Matulaitis July 23, 1957 OTHER REFERENCES Amer. Mach. Spec. Rep. 356, 1954, 6 pp. 

